Carpenter Bee Identification
Most carpenter bees, Xylocopa spp., are large and robust insects resembling bumble bees. They are usually about 1 inch long and colored a metallic blue-black with green or purplish reflections. They differ from bumble bees in that their abdomen is shiny with fringes of hairs on some segments. Males of some species are lighter colored, ranging into golden or buff hues. Female carpenter bees bore into sound wood or sometimes into decaying wood to make nests. Nests usually consist of tunnels ½ inch in diameter and 6 to 10 inches deep that are partitioned into several chambers, each containing an egg and a supply of food (pollen). The tunnel entrance has been noted to slope upward, commonly a near vertical opening in the side or bottom surface of a wooden member. Carpenter bees may use old tunnels for their nests, which they sometimes enlarge; several bees may use a common entry hole connecting to different tunnels. Over a period of time, tunnels may extend as far as 10 feet into wood timbers. Tunnels are vacated after the brood's larval and pupal stages complete their development. Development from egg to adult may take about 3 months. Carpenter bees overwinter as adults, often in old tunnels, and there is only one generation a year.
Carpenter bees cause damage to wooden structures by boring into timbers and siding to prepare nests. The nests weaken structural wood and leave unsightly holes and stains on building surfaces. Woodpeckers feeding on carpenter bee larvae multiply the damage by tearing open the nests. Sound, undecayed wood without paint or bark is usually selected for nests. Farm structures that feature exposed unpainted rafters are particularly susceptible to infestation. Since the bees do not eat the wood, lumber that is naturally insect resistant or treated to resist insects is susceptible to infestation. In testing and field observations, carpenter bees were most attracted to Juniperus virginiana wood of the Cupressaceae family, presumably since the aromatic insect-resistant nature of the wood repels parasites of the bees. Standing dead Juniperus virginiana trees are conspicuous as sites of carpenter bee colonies in the southeastern United States. Carpenter bees also frequently attack dead wood on trees or lumber from southern yellow pine, white pine, California redwood, cedar, Douglas fir, cypress, mimosa, mulberry, ash, and pecan trees. They avoid most harder woods. The presence of carpenter bees around buildings and wooden structures can be annoying or even frightening; however, males cannot sting and females rarely attack.